This invention relates generally to methods and apparatus for attaching soft tissue to bone, and more particularly to anchors and methods for securing connective tissue, such as ligaments or tendons, to bone. The invention has particular application to arthroscopic surgical techniques for reattaching the rotator cuff to the humeral head, in order to repair the rotator cuff.
It is an increasingly common problem for tendons and other soft, connective tissues to tear or to detach from associated bone. One such type of tear or detachment is a xe2x80x9crotator cuffxe2x80x9d tear, wherein the supraspinatus tendon separates from the humerus, causing pain and loss of ability to elevate and externally rotate the arm. Complete separation can occur if the shoulder is subjected to gross trauma, but typically, the tear begins as a small lesion, especially in older patients.
To repair a torn rotator cuff, the typical course today is to do so surgically, through a large incision. This approach is presently taken in almost 99% of rotator cuff repair cases. There are two types of open surgical approaches for repair of the rotator cuff, one known as the xe2x80x9cclassic openxe2x80x9d and the other as the xe2x80x9cmini-openxe2x80x9d. The classic open approach requires a large incision and complete detachment of the deltoid muscle from the acromion to facilitate exposure. The cuff is debrided to ensure suture attachment to viable tissue and to create a reasonable edge approximation. In addition, the humeral head is abraded or notched at the proposed soft tissue to bone reattachment point, as healing is enhanced on a raw bone surface. A series of small diameter holes, referred to as xe2x80x9ctransosseous tunnelsxe2x80x9d, are xe2x80x9cpunchedxe2x80x9d through the bone laterally from the abraded or notched surface to a point on the outside surface of the greater tuberosity, commonly a distance of 2 to 3 cm. Finally, the cuff is sutured and secured to the bone by pulling the suture ends through the transosseous tunnels and tying them together using the bone between two successive tunnels as a bridge, after which the deltoid muscle must be surgically reattached to the acromion. Because of this maneuver, the deltoid requires postoperative protection, thus retarding rehabilitation and possibly resulting in residual weakness. Complete rehabilitation takes approximately 9 to 12 months.
The mini-open technique, which represents the current growing trend and the majority of all surgical repair procedures, differs from the classic approach by gaining access through a smaller incision and splitting rather than detaching the deltoid. Additionally, this procedure is typically performed in conjunction with arthroscopic acromial decompression. Once the deltoid is split, it is retracted to expose the rotator cuff tear. As before, the cuff is debrided, the humeral head is abraded, and the so-called xe2x80x9ctransosseous tunnelsxe2x80x9d, are xe2x80x9cpunchedxe2x80x9d through the bone or suture anchors are inserted. Following the suturing of the rotator cuff to the humeral head, the split deltoid is surgically repaired.
Although the above described surgical techniques are the current standard of care for rotator cuff repair, they are associated with a great deal of patient discomfort and a lengthy recovery time, ranging from at least four months to one year or more. It is the above described manipulation of the deltoid muscle together with the large skin incision that causes the majority of patient discomfort and an increased recovery time.
Less invasive arthroscopic techniques are beginning to be developed in an effort to address the shortcomings of open surgical repair. Working through small trocar portals that minimize disruption of the deltoid muscle, a few surgeons have been able to reattach the rotator cuff using various bone anchor and suture configurations. The rotator cuff is sutured intracorporeally and an anchor is driven into bone at a location appropriate for repair. Rather than thread the suture through transosseous tunnels which are difficult or impossible to create arthroscopically using current techniques, the repair is completed by tying the cuff down against bone using the anchor and suture. Early results of less invasive techniques are encouraging, with a substantial reduction in both patient recovery time and discomfort.
Unfortunately, the skill level required to facilitate an entirely arthroscopic repair of the rotator cuff is inordinately high. Intracorporeal suturing is clumsy and time consuming, and only the simplest stitch patterns can be utilized. Extracorporeal knot tying is somewhat less difficult, but the tightness of the knots is difficult to judge, and the tension cannot later be adjusted. Also, because of the use of bone anchors to provide a suture fixation point in the bone, the knots that secure the soft tissues to the anchor by necessity leave the knot bundle on top of the soft tissues. In the case of rotator cuff repair, this means that the knot bundle is left in the shoulder capsule where it is able to be felt by the patient postoperatively when the patient exercises the shoulder joint. So, knots tied arthroscopically are difficult to achieve, impossible to adjust, and are located in less than optimal areas of the shoulder. Suture tension is also impossible to measure and adjust once the knot has been fixed. Consequently, because of the technical difficulty of the procedure, presently less than 1% of all rotator cuff procedures are of the arthroscopic type, and are considered investigational in nature.
Another significant difficulty with current arthroscopic rotator cuff repair techniques are shortcomings related to currently available suture anchors. Suture eyelets in bone anchors available today, which like the eye of a needle are threaded with the thread or suture, are small in radius, and can cause the suture to fail at the eyelet when the anchor is placed under high tensile loads.
There are various bone anchor designs available for use by an orthopedic surgeon for attachment of soft tissues to bone. The basic commonality between the designs is that they create an attachment point in the bone for a suture that may then be passed through the soft tissues and tied, thereby immobilizing the soft tissue. This attachment point may be accomplished by different means. Screws are known for creating such attachments, but suffer from a number of disadvantages, including their tendency to loosen over time, requiring a second procedure to later remove them, and their requirement for a relatively flat attachment geometry.
Another approach is to utilize the difference in density in the cortical bone (the tough, dense outer layer of bone) and the cancellous bone (the less dense, airy and somewhat vascular interior of the bone). There is a clear demarcation between the cortical bone and cancellous bone, where the cortical bone presents a kind of hard shell over the less dense cancellous bone. The aspect ratio of the anchor is such that it typically has a longer axis and a shorter axis and usually is pre-threaded with a suture. These designs use a hole in the cortical bone through which an anchor is inserted. The hole is drilled such that the shorter axis of the anchor will fit through the diameter of the hole, with the longer axis of the anchor being parallel to the axis of the drilled hole. After deployment in to the cancellous bone, the anchor is rotated 90xc2x0 so that the long axis is aligned perpendicularly to the axis of the hole. The suture is pulled, and the anchor is seated up against the inside surface of the cortical layer of bone. Due to the mismatch in the dimensions of the long axis of the anchor and the hole diameter, the anchor cannot be retracted proximally from the hole, thus providing resistance to pull-out. These anchors still suffer from the aforementioned problem of eyelet design that stresses the sutures.
Still other prior art approaches have attempted to use a xe2x80x9cpop rivetxe2x80x9d approach. This type of design requires a hole in the cortical bone into which a split shaft is inserted. The split shaft is hollow, and has a tapered plug leading into its inner lumen. The tapered plug is extended out through the top of the shaft, and when the plug is retracted into the inner lumen, the tapered portion causes the split shaft to be flared outwardly, ostensibly locking the device into the bone.
Other methods of securing soft tissue to bone are known in the prior art, but are not presently considered to be feasible for shoulder repair procedures, because of physicians"" reluctance to leave anything but a suture in the capsule area of the shoulder. The reason for this is that staples, tacks, and the like could possibly fall out and cause injury during movement. As a result of this constraint, the attachment point often must be located at a less than ideal position. Also, the tacks or staples require a substantial hole in the soft tissue, and make it difficult for the surgeon to precisely locate the soft tissue relative to the bone.
As previously discussed, any of the anchor points for sutures mentioned above require that a length of suture be passed through an eyelet fashioned in the anchor and then looped through the soft tissues and tied down to complete the securement. Much skill is required, however, to both place the sutures in the soft tissues, and to tie knots while working through a trocar under endoscopic visualization.
There have been attempts to solve some of the problems that exist in current anchor designs. One such approach is disclosed in U.S. Pat. No. 5,324,308 to Pierce. In this patent, there is disclosed a suture anchor that incorporates a proximal and distal wedge component having inclined mating faces. The distal wedge component has two suture thread holes at its base through which a length of suture may be threaded. The assembly may be placed in a drilled hole in the bone, and when tension is placed on the suture, the distal wedge block is caused to ride up against the proximal wedge block, expanding the projected area within the drilled hole, and locking the anchor into the bone. This approach is a useful method for creating an anchor point for the suture, but does not in any way address the problem of tying knots in the suture to fix the soft tissue to the bone.
The problem of placing sutures in soft tissues and tying knots in an endoscopic environment is well known, and there have been attempts to address the problem and to simplify the process of suture fixation. One such approach is disclosed in U.S. Pat. No. 5,383,905 to Golds et al. The patent describes a device for securing a suture loop about bodily tissue that includes a bead member having a longitudinal bore and an anchor member adapted to be slidably inserted within the bore of the bead member. The anchor member includes at least two axial compressible sections which define a passageway to receive two end portions of a suture loop. The axial sections collapse radially inwardly upon insertion of the anchor member within the bore of the bead member to securely wedge the suture end portions received within the passageway.
Although the Golds et al. patent approach utilizes a wedge-shaped member to lock the sutures in place, the suture legs are passing through the bore of the bead only one time, in a proximal to distal direction, and are locked by the collapsing of the wedge, which creates an interference on the longitudinal bore of the anchor member. Also, no provision is made in this design for attachment of sutures to bone. The design is primarily suited for locking a suture loop, such as is used for ligation or approximation of soft tissues.
An approach that includes bone attachment is described in U.S. Pat. No. 5,584,835 to Greenfield. In this patent, a two part device for attaching soft tissue to bone is shown. A bone anchor portion is screwed into a hole in the bone, and is disposed to accept a plug that has been adapted to receive sutures. In one embodiment, the suture plug is configured so that when it is forced into its receptacle in the bone anchor portion, sutures that have been passed through an eyelet in the plug are trapped by friction between the wall of the anchor portion and the body of the plug portion.
Although there is some merit to this approach for eliminating the need for knots in the attachment of sutures to bone, a problem with being able to properly set the tension in the sutures exists. The user is required to pull on the sutures until appropriate tension is achieved, and then to set the plug portion into the bone anchor portion. This action increases the tension in the sutures, and may garrot the soft tissues or increase the tension in the sutures beyond the tensile strength of the material, breaking the sutures.
A disclosure that incorporates bone attachment and eliminates knot tying is set forth in U.S. Pat. No. 5,702,397 to Goble et al. One embodiment, in particular, is shown in FIG. 23 of that patent and includes a bone anchor that has a threaded body with an inner cavity. The cavity is open to one end of the threaded body, and joins two lumens that run out to the other end of the threaded body. Within the cavity is disposed a gear, journaled on an axle. A length of suture is threaded through one lumen, around the gear, and out through the other lumen. A ball is disposed within the cavity to ride against a tapered race and ostensibly lock the suture in place. What is not clear from the patent disclosure is how the force D shown as the tension in the suture would lock-the ball into the race. Although this embodiment purports to be a self-locking anchor adapted for use in blind holes for fixing sutures into bone, the construct shown is complicated, and does not appear to be adequate to reliably fixate the suture.
What is needed, therefore, is a new approach for repairing the rotator cuff or fixing other soft tissues to bone, wherein suture tension can be adjusted and possibly measured, the suture resides completely below the cortical bone surface, there is no requirement for the surgeon to tie a knot to attach the suture to the bone anchor, and wherein the procedure associated with the new approach is better for the patient, saves time, is uncomplicated to use, and easily taught to practitioners having skill in the art.
The present invention solves the problems outlined above by providing innovative bone anchor and connective techniques which permit a suture attachment which lies entirely beneath the cortical bone surface. In the present state of the art, the sutures which are passed through the tissues to be attached to bone typically are threaded through a small eyelet incorporated-into the head of the anchor and then secured by tying knots in the sutures. Endoscopic knot tying is an arduous and technically demanding task. Therefore, the present invention discloses devices and methods for securing sutures to a bone anchor without the requirement of knot tying.
In one embodiment, the suture legs, after having been placed into soft tissues to be anchored to bone, are threaded through the anchor and then through a floating wedge block located at the distal end of the anchor. The wedge block is configured such that it has a hollow lumen through the center, and a conically tapered outer surface. The distal end of the wedge block is the wider end of the cone, and the transition from the inside diameter created by the hollow lumen and the outside diameter created by the conical surface includes smooth radii for dressing the sutures threaded through the hollow lumen. The sutures are passed back around the outside of the wedge block such that they rest on the conical surface. They are then re-threaded in the opposite direction back through the anchor, exiting the anchor at the proximal end thereof. The anchor is then inserted into the bone, and secured. The distal end of the anchor is tapered to match the taper of the conical surface on the wedge block. When tension is placed on the legs of the suture passing back out of the anchor, the suture is drawn through the hollow center lumen, around the distal end of the wedge block, and back out of the anchor. This tension tends to cause the wedge block to force its way back up into the anchor body, and a means to prevent this may be employed. Such means may include any structure that selectively holds the wedge block separate from the anchor body.
At this juncture, by pulling on the suture legs, any slack in the sutures is removed, and the soft tissues are drawn toward the anchor. When the soft tissues are in the desired orientation, relative to the bone to which they are to be attached, the structure holding the wedge block is removed, and the back tension on the sutures pulls the wedge block into the matching taper in the anchor body, maintaining the compressive force on the suture legs.
In another embodiment, the wedge block may be adapted to have a U-shaped channel along one side of the wedge, and a tapered face along the opposite side of the wedge. The U-shaped channel communicates with the tapered face via a large radius surface that transitions and blends the channel face to the tapered face. The wedge is configured such that it may be placed inside of a hollow cylinder with a tapered face that protrudes into the interior of the cylinder and is configured to mate with the taper of the wedge. The wedge is adapted to permit two legs of the suture to be threaded through the anchor body, and along the U-shaped channel to the distal end of the anchor, wherein the sutures are drawn around the radiused surface and onto the tapered surface of the wedge on the opposite side. The sutures then pass back out of the proximal end of the anchor. As before, the suture legs may pass freely around the tapered wedge block until such time as tension in the bound legs pulls the wedge block back up into the tapered body of the anchor, and locks the suture in place.
Thus, with the above-described suture locking system, suture failure rates are dramatically reduced over conventional techniques because of the increased radius over which the suture is loaded, and the inventive procedures are significantly easier to perform than conventional techniques because of the elimination of knot tying.
More particularly, there is provided a bone anchor device for attaching connective tissue to bone, which comprises an outer body, and a lumen extending axially through the outer body. Inner walls which define the lumen in a proximal portion of the outer body extend inwardly relative to inner walls which define the lumen in a portion of the outer body distal to the proximal portion. A wedge member is advantageously disposed in a distal end of the lumen, distal to the inwardly extending lumen wall portion, which has outer walls that taper inwardly in a proximal direction therealong. The wedge member is axially movable in the lumen distal end.
In one preferred embodiment, a lumen extends axially through the wedge member, for receiving a suture therein. The wedge member preferably comprises a distal end having a curved surface, and the tapered proximal surface of the wedge member and the inwardly extending lumen internal wall together define a tapered distal lumen which communicates with the lumen.
A suture extends through the lumen and around the distal curved surface of the wedge member, and includes a free end extending proximally out of the bone anchor device and a bound end attached to soft tissue to be secured to the bone, wherein when the free end is placed in tension by a proximally directed force, the suture travels about the wedge member until increased tension on the bound end causes the suture to move the wedge member axially in a proximal direction, the proximal axial travel of the wedge member continuing until the proximal surface of the wedge member has moved into sufficient proximity to the inwardly extending internal lumen wall to pinch a length of the suture in the tapered distal lumen.
In another aspect of the invention, there is provided a bone anchor device for attaching connective tissue to bone, which comprises an outer body and a lumen extending axially through the outer body. Inner walls which define the lumen taper in a proximal portion of the outer body extend inwardly relative to inner walls which define the lumen in a portion of the outer body distal to the proximal portion. A suture clamping member, consisting of a wedge member, is axially movable in the lumen.
In still another aspect of the invention, there is provided a bone anchor device for attaching connective tissue to bone, which comprises an outer body having a lumen extending axially therethrough. Inner walls which define the lumen in a proximal portion of the outer body extend inwardly relative to inner walls which define the lumen in a portion of the outer body distal to the proximal portion. A suture clamping member comprising a wedge member is axially movable in the lumen distal portion. A suture extends through the lumen and around a distal surface of the wedge member, which includes a free end extending proximally out of the bone anchor device and a bound end attached to soft tissue to be secured to the bone. When the free end is placed in tension by a proximally directed force, the suture travels about the wedge member until increased tension on the bound end causes the suture to move the wedge member axially in a proximal direction, the proximal axial travel of the wedge member continuing until the proximal surface of the wedge member has moved into sufficient proximity to the inwardly extending internal lumen wall to pinch a length of the suture therebetween.
In another aspect of the invention, there is provided a bone anchor device for attaching connective tissue to bone, which comprises an outer body having an open distal end, and a lumen extending axially through the outer body. Inner walls which define the lumen in a proximal portion of the outer body extend inwardly relative to inner walls which define the lumen in a portion of the outer body distal to the proximal portion. A suture clamping member having an outer surface is disposed in the lumen distal end and is axially movable therein. Advantageously, complementary engaging structure is disposed on each of the suture clamping member outer surface and the lumen inner surface for retaining the suture clamping member in the lumen distal end when the bone anchor device is not in a portion of bone. This complementary engaging structure preferably comprises a pin disposed on one of the suture clamping member outer surface and the lumen inner surface, and a recess for receiving the pin disposed on the other of the suture clamping member outer surface and the lumen inner surface.
In yet another aspect of the invention, there is provided a bone anchor device for attaching connective tissue to bone, which.comprises an outer body having an outer surface, and a lumen extending axially through the outer body. Inner walls which define the lumen in a proximal portion of the outer body extend inwardly relative to inner walls which define the lumen in a portion of the outer body distal to the proximal portion. A suture clamping member is disposed in the lumen distal portion and is axially movable therein. Additionally, at least one outwardly extendable rib is disposed on the outer body outer surface for anchoring the outer body into surrounding bone.
In still another aspect of the invention, there is provided a bone anchor device for attaching connective tissue to bone, which comprises a distal wedge anchor portion comprising an outer body having an outer surface, on which a outwardly deployable anchoring element is situated. Additionally, a proximal driver portion is connected to the distal wedge anchor portion at a proximal end thereof, which includes an actuator for deploying the anchoring element outwardly. Advantageously, the connection between the proximal driver portion and the distal wedge anchor portion is releasable once the anchoring element has been deployed. In a preferred embodiment, this is accomplished because of a designed failure point in the connection between the proximal driver portion and the distal wedge anchor portion, so that upon deployment of the anchoring element outwardly, additional force may be applied to separate the driver portion from the anchor portion so that only the driver portion may be proximally removed from the patient""s body.
In yet another aspect of the invention, there is disclosed a method for securing connective tissue to bone, which comprises securing a first end of a length of suture to a portion of soft tissue to be attached to a portion of bone. A second end of the length of suture is threaded through a lumen in an outer body of a bone anchor device and about an axially movable suture clamping member disposed in a distal portion of the lumen. The outer body is placed in a blind hole disposed in the portion of bone, and the second end of the length of suture is pulled proximally, so that the suture travels about the axially movable suture clamping member and draws the first end of the length of suture toward the bone anchor device, thereby securing the portion of soft tissue snugly to the portion of bone. Advantageously, when the tension on the first end of the length of suture increases, as the portion of soft tissue is bound to the portion of bone, the suture clamping member is pulled proximally toward inwardly extending walls defining a portion of the lumen, thereby clamping a portion of the length of suture between the inwardly extending lumen walls and the suture anchoring device.
Additional steps in the preferred method include anchoring the outer body in the blind hole, preferably by deploying ribs disposed on an outer surface of the outer body to an outwardly extended position, into surrounding cancellous bone, and cutting a portion of the suture second end to complete the procedure.
In another aspect of the invention, there is disclosed a method for securing connective tissue to bone, which comprises securing a first end of a length of suture to a portion of soft tissue to be attached to a portion of bon e, and threading a second end of the length of suture through a lumen in an outer body of a bone anchor device and about an axially movable suture clamping member disposed in a distal portion of the lumen. The bone anchor device is inserted into a blind hole disposed in the portion of bone, and a deployable anchoring member disposed on an outer surface of the outer body is extended outwardly to secure the bone anchor device in surrounding bone. Following this step, a driver portion of the bone anchor device is separated from the outer body and withdrawn from the patient""s body. Then, the second end of the length of suture is pulled proximally, to secure the portion of soft tissue properly to the portion of bone and to anchor the suture in the outer body by moving the suture clamping member axially to a suture clamping position.
In still another aspect of the invention, there is provided a bone anchor device for attaching connective tissue to bone, which comprises a body having a longitudinal axis, a distal end, and a proximal end. A surface on the body distal end slopes inwardly toward the longitudinal axis from a distal portion of the surface toward a proximal portion thereof. A suture anchoring member which is movable axially toward and away from sloping surface forms a part of the bone anchor device. The suture anchoring member s a distal end surface and opposing axial surfaces, wherein the distal end and opposing axial surfaces all comprise suture receiving surfaces for contacting suture material wrapped thereabout. In essence, this means that in use, a length of suture material will be wrapped about the suture anchoring member in such a manner that the length of suture material will be in physical contact with all of the distal end surface and opposing side surfaces. In preferred embodiments, one of the opposing axial surfaces is sloped so that a width of the suture anchoring member (i.e. a dimension of the suture anchoring member which is transverse to the longitudinal axis) tapers from a distal end to a proximal end thereof.
As has been discussed supra, the sloped axial surface and the inwardly sloped body distal end surface together define a tapered distal lumen.
Now, it is to be understood that the above described invention is particularly suited to locking sutures that have been passed through soft tissues and are to be anchored to bone. The creation of an anchor point within the bone is outside the scope of this invention, although many alternative methods of anchoring suture to bone are contemplated. For example, some currently preferred methods are discussed in U.S. patent application Ser. No. 09/616,802, entitled Method and Apparatus for Attaching Connective Tissues to Bone Using a Suture Anchoring Device, filed on Jul. 14, 2000. The referenced application is commonly assigned with the present application, and is incorporated by reference in its entirety herein. Other prior art anchors, such as screws, moly bolts, and pop rivets may be adapted for use with the present invention as well.